How coronavirus spreads twice as far on trains, buses, public transport

New research shows coronavirus can be transmitted twice as far on public transport, spreading even after an infected person has left an area.

As countries around the world take increasingly drastic measures to slow the coronavirus outbreak, a new study has found the disease can travel twice as far as the official “safe distance” on public transport.

The research, completed by a team of Chinese government epidemiologists, found that a passenger – unaware that they had coronavirus – infected up to 13 other people travelling on the same bus in a matter of hours.

The virus that causes COVID-19 can linger in the air for at least 30 minutes and travel up to 4.5m – further than the distance people have been advised to keep from each other by health authorities around the world.

“It can be confirmed that in a closed environment with airconditioning, the transmission distance of the new coronavirus will exceed the commonly recognised safe distance,” the researchers wrote in a paper published in Practical Preventive Medicine last Friday.

RELATED: Follow the latest coronavirus updates

The paper also highlighted the risk that the virus – which has infected more than 110,000 people around the world and at least 100 people in Australia – could remain afloat even after the carrier had left the bus.

Based on a local outbreak case on January 22 during the peak Lunar New Year travel season, the research followed a passenger who boarded a fully booked long-distance bus and sat in the second row from the back.

The passenger, known as “A”, already felt unwell. But China was yet to declare the coronavirus outbreak a national crisis, so the passenger did not wear a mask, nor did the driver or most of the other passengers on the 48-seat bus.

RELATED: Should I cancel my travel plans?

The scientists said the study highlighted how important it was to wear face masks in public. Picture: Raul Arboleda/AFP

Lead author of the study Hu Shixiong, who works for the Hunan Provincial Centre for Disease Control and Prevention, said security camera footage showed patient “A” did not interact with others throughout the four-hour ride.

Yet, by the time the bus stopped at the next city, the virus had already jumped from “A” to seven other passengers.

These passengers weren’t only sitting relatively close to “patient zero”. Some were six rows – roughly 4.5m – away, and all later tested positive, including one passenger who displayed no symptoms of the disease.

After these passengers left, another group got on the bus about half an hour later.

One passenger sitting in the front row, who was also not wearing a mask, became infected. Mr Hu said this patient was likely to have inhaled the particles breathed out by the infected passengers from the previous group.

RELATED: How virus ripped across Sydney

“The possible reason is that in a completely enclosed space, the airflow is mainly driven by the hot air generated by the airconditioning. The rise of the hot air can transport the virus-laden droplets to a greater distance,” the scientists noted.

As for patient “A”, after getting off the first bus, they got on a minibus and travelled for another hour, infecting two new passengers.

By the time the study was finished in mid-February, patient “A” had infected at least 13 people.

The scientists said the study proved the importance of washing hands and wearing a mask in a public place despite advice from other health officials that wearing a face mask isn’t necessary unless you’re unwell.

“Our advice is to wear a face mask all the way (through the bus ride),” they wrote in the paper, which found that those on-board the bus who did wear a face mask did not become infected.

“When riding on more closed public transport such as subways, cars, planes, etc. you should wear a mask all the time and, at the same time, minimise the contact between your hands and public areas and avoiding touching your face before cleaning.”

RELATED: How deadly coronavirus spreads

The researchers said the interiors of buses should be disinfected once or twice a day. Picture: Mykola Tys/AP

The researchers found that the disease could last for days on surfaces where respiratory droplets land, raising the risk of transmission if an unsuspecting person touches it and then rubs their face or hands.

The length of time coronavirus lasts on a surface depends on factors such as temperature and the types of surface. On a bus, where common surfaces are made from materials like glass, fabric, metal or plastic, the virus can survive for two to three days.

As well as urging passengers to wear face masks, the scientists suggested improved sanitation on public transport, adjusting the airconditioning to maximise the volume of fresh air supplied, and cleaning and disinfecting bus interiors once or twice a day.